Generally a hot melt adhesive to be applied in a thermally fluid state takes a solid form at room temperature. The hot melt adhesive is generally provided in the form of a block and is heated to become melted before use. Because of such properties, the hot melt adhesive poses various problems in handling and packaging. The block of hot melt adhesive solid not only sticks or adheres to our hands or mechanical handling devices but also combines our hands or mechanical handling devices with each other. Further the block picks up dirt and contaminants. In addition, a hot melt adhesive having an adhesive surface is used as accommodated in a paper container or a plastic container which is made mold-releasing with silicone or the like to avoid mutual adhesion and to improve operational efficiency.
However, such packaging method requires removal and disposal of packaging materials in using the packaged hot melt adhesive. That is, the method involves labor and is likely to contaminate the environment with waste.
From viewpoints of saving of resources and environmental conservation, methods have been carried out which comprise wrapping the hot melt adhesive with a polyolefin film instead of using such container and melting the wrapped without removing the polyolefin film. However, these methods have caused troubles. Since the polyolefin film has a relatively high softening point, it takes a long time to uniformly dissolve the polyolefin film in molten hot melt adhesive composition. Due to properties of polyolefin, properties of hot melt adhesive are impaired and heat stability in a tank of hot melt adhesive is lowered. Another method was proposed wherein wax or the like is sprayed over the inside of a metal container and a hot melt adhesive is filled into the wax-coated metal container, thereby eliminating the adhesion from the surface of the adhesive. However, the side of the metal container is coated with a lesser amount of wax than the wax applied to the bottom of the metal container. That is, the wax is deposited on the bottom and on the side of the metal container at an irregular ratio. Furthermore, the hot melt adhesive is handled in a high temperature environment wherein the adhesive is flowable, so that the molten wax is dissolved and penetrated into the hot melt adhesive. Namely, the adhesive is readily affected by the temperature, and incorporates an increased amount of adhesion inhibitor.
To overcome these problems, it is necessary to minimize the ratio of an adhesion inhibitor such as wax by coating the largest possible hot melt adhesive block with the adhesion inhibitor and by applying a film over portions of blocks to be contacted with each other to completely separate the adhesive blocks from each other. More specifically, a method is being investigated wherein wax is sprayed over a tray having a shape such as cylinder and rectangular parallelepiped and a hot melt adhesive is filled thereinto and molded. However, if the wax is applied in a lesser amount, it is difficult to separate the tray from the hot melt adhesive. On the other hand, this method has a drawback. A large amount of wax sprayed facilitates separation of the tray from the adhesive but may be mingled with the adhesive, thereby affecting properties of the adhesive.
A further method was proposed wherein a hot melt adhesive is continuously forced out from an extrusion molding machine and is cut to a proper length to mold pellets, followed by coating the pellets with wax. However, the hot melt adhesive to be produced by this method is limited to relatively small size blocks. To produce large size hot melt adhesive blocks, a large scale extrusion molding machine is required, and a high equipment cost is incurred. Namely the method is improper for commercial manufacture.
Objects of the present invention are to provide a hot melt adhesive solid and a method of producing the hot melt adhesive solid, the method being capable of overcoming the foregoing problems of conventional packaging methods which can prevent the adhesion of hot melt adhesive blocks to each other, the method being capable of minimizing the proportion of a different material such as a film mingling with the hot melt adhesive, preventing the hot melt adhesive blocks from adhering to each other and achieving a high operational efficiency, and to provide methods of packaging and transporting hot melt adhesive blocks wherein the amount of waste derived from packaging materials can be suppressed.